Fume-absorber for electric lamps.



{HATE ur mums mm an Huua 1mm Y W. R. MOTT. FUME ABSORBER FOR'ELE-CTRIC LAMPS.

APPLICALIDN FILED mmr. 1917- 1,297,387;v PatentdMaf. I8,1919.

Nu FuMB 958mm 160 z'un s un 41in sin sin min sin sin 'anuu HOURS BUHNINB DP LAMP INVENTORI.

ATTORNEY 1 UNITED STATES PATENT OFFICE.

WILLIAM ROY MOT'I, OF LAKEWOOD, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO NATIONAL CARBON COMPANY, INC., A CORPORATION OF NEW YORK.

FUME-ABSORBER FOR ELECTRIC LAMPS.

Specification of Letters Patent.

Patented Mar. 18, 1919.

Application filed January 2'7, 1917. Serial No. 144,865.

To all whom it may concern:

Be it known that I, WILLIAM R. Mo'r'r, a citizen of the United States, residing at Lakewood, in the county of Cuyahoga and State of Ohio, have invented a certain new and useful Improvement in Fume-Absorbers for Electric Lamps, of whichthe following is a full, clear, and exact description.

This invention relates to flame arc lamps. As is well known such lamps employ electrodes having certain salts, oxids and other materials to increase the luminosity of the arc. Since it is essential that these materials volatilize and pass into the arc, more or less difficulty has been experienced from condensation on the glass globes and other parts of the lamps.

For most purposes, fluorid compounds (such as calcium 'fiuorid, rare-earth fluorids,

etc.) are indispensable for the flame arc electrodes, and these with the moisture of the air have a tendency to form at the are some hydrofluoric acid (HF) which etches the glass globe and gradually decreases its power to transmit light, and may even wear out the globe. Alkaline silicates in the electrodes lessen etching, as the fumes are diminished by acting on such silicates rather than on the silicates in the glass. For this reason etching with cored electrodes is not very pronounced. With solid flamers,

however, sufiicient alkaline silicates often cannot be used on account of slagging and other difficulties. It is with lamps employing such electrodes that this invention is of particular value.

The way that hot fluorids react with water vapor in the air to produce hydrofluoric acid in the are, or in its vicinity, will be understood from the following equations, those iven being typical of the reaction of other fluorids, the first reaction being partly reversible under usuallamp conditions:

The above reactions can be readily shownto take place to a considerable extent by 1 merely heating the fluorids to red heat in a ally employed above ing water vapor. From this it follows that It is important to eliminate not only the fluorin compounds, but also the hydrogen compounds which may combine with oxygen to form water. With this water and hydrogen containing materiaLa cycle of processes is established so that a little causes a great deal of etching. The first part of the cycle is given by the above equations and last part is the action of the hydrofluoric acid on .the glass which is a composite silicatecontainirmaterial. The reaction on potassium silicate is given below by way of example. K OSiO +GHF=K SiF +3H O From this reaction it will be seen that water is formed which will start on its destructive cycle as soon as it evaporates.

It has been proposed to place magnesium oxid (or carbonate) in the condenser usuthe flame are to absorb glass etching fumes, but I have found that certain compounds far exceed the ability of these compounds in this respect. The reactions with the magnesium oxid or carbonate returns the hydrogen to the circuit in the form of water in practically undiminished quantity. The reactions referred to are as follows:

The materials that I have discovered to be especially good are those that are capable of absorbing, alone or jointly, both the fluorin part and a considerable part of the hydrogen constituent of the vapors in the arc chamber. In the preferred form of my invention, the same substance absorbs both fluorin and more or less hydrogen in reacting with hydrogen. fl'uorid (HF) to produce complex fluorids that are by nature practically inert with respect to'etching of glass or elseare prevented from reaching the globe on account of their remaining trapped in the condenser. Boron compounds have a marked tendency to form such complex compounds, for instance borofluorids, and in general I prefer to utilize them for this purpose, but the desired property is possessed-by certain compounds of otassium, sodium and barium which will lie specifically referred to later. 3

placed as a transparent coating on the glass,

The most eflicient (under service tests) of the boron compounds, I have found to be fused boric acid (chiefly boron oxid.

'.(B O which reacts on the hydrofluoric acid vapors substantially in accordance with the following equation adds but little Water to the lamp atmos- .15

phere. Other intermediate products are formed, but these facilitate the speed of reaction and also have marked power to absorb water. Hydroborofiuoric acid is .practically non-volatile under the usual condenser conditions', and therefore the resulting product is largely retained in the condenser and does not injure'the lamp globe or the delicate parts of the lamp mechanism. I have found that the beneficial effects of boron materials are obtained even when as the etchingaction of potassium fluorid and hydrofluoric acid, for example, are greatly retarded. Y I

Borates also possess the desired characteristic of combining with-hydrogen fluorid fumes, but these are; not so efficient under servlce conditions 1n this respect as the bone oxidr By way of example, I may mention the borates of sodium, potassium and calcium whichreact with the hydrofluoric acid in accordance with the following equations,

the equation for, potassium borate being. similar .to that ofsodium: I

- There are a number of calcium borates,

act with hydrogen fluorid to render it harmless to, a more or less extent, such as boron nitridand boron fluorid Which/react in accordance with the following equ'ations'to produce complex fiuorids:

. BN+4HF=NH BF, a F8+ F=HBF. The boron nitrid ispeculiarly efiicient in the weight of hydrofluoric acid absorbed both as to fluorin and as to hydrogen.

Still other materials capable of forming complex fluorin compounds in the Warm condenser under service conditions are sodium,

potassium and barium fluorids. Y My tests 'with sodium fluorid and potassium salts show them to be especially good, though notequal to boron oxid. These react in the fol- The products of the above reactions are quite stable even at fairly high temperatures. Hence thereisno tendency to decompose at the temperature obtaining in'the lamp condenser. Oxy-compounds of the above metallic elements, also can be used to form double fluorin compounds in some cases. Also fluorids of other metals, such as caesium, rubidium and barium, accomplish the desired result.

In the single figure of the drawing I have.

' shown various etching curves, the ordinates .being the rate of etching in milligrams per 20 hour unit of time, and the abscissas hours of actual burning of the lamp. In all cases the conditions are identical. From thesecurves it will be seen thatiboric oxid is much superior to the other materials in fume absorbing properties. As previously stated, I

acid in the lamp, and find that it is best to fuse this material in order to dehydrate it more or less before placing it in lamp parts to which are fumes can come. While hydrated boric'oxid or borici acid (H BO could be used, it is not so desirable as the dehydrated material. The invention,- however, includes both forms as well as material containing free or combined oxyboron compounds, as these will secure the desired results to a greater or less extent.

While water Vapor in 'the'lamp greatly promotes etching, 'I have found that a little water in the lampactually decreases etch ing, when boric oxidis used. The reason for this is probably because the water softens the crust on the oxid and permits the chemical action to proceed at an undiminished rate. In other words, the beneficial effect of water on the boric oxid more than ofisets the detrimental effect of enhancing the formation of hydrofluoric acid. Q

While in the claims I refer to my improved products as fume absorbers, it must be'understood that this is used for lack of a better term rather than for its accuracy.

To prevent or-reduce etching, I also use dehydrating agents, such as P 0 and other preferto use boric' phosphoric oxycompounds for example, as I Having described my invention, what I claim is: e

1. In electric arc lamps, electrodes adapted to form an arc containing glass-etching fiuorids and a fume absorber containing a material adapted to combine with said fluorids to produce complex fluorids inactive toward glass.

2. In electric arc lamps, electrodes adapted to form an arc containing glass-etching V fluoridsnand a .fume absorber containing a material adapted to combine with said fiuorids to produce complex acid-fluorids inactive toward glass.

3. In electric arc lamps, electrodes adapted to form an arc containing glass-etching fiuorids and a fume absorber containing boron compounds adapted to combine with said fluorids to form complex fluorids inactive toward glass.

4;. In electric arc lamps, electrodes adapted to form an arc containing glass-etching fiuorids and a fume absorber containing boric oxid adapted to combine with said fluorids to form complex boro-fiuorids inactive toward glass.

In electric arc lamps, electrodes adapted to form an arc cont-aining glass-etching V fluorids and a fume absorber containing fused .boric oxid adapted to combine with said fiuorids to form hydro-fluo-boric acid.

In testimony whereof, I hereunto alfix my signature.

WM. ROY MOTT. 

